They are worth the investment if you commit yourself to using them regularly and get inventive in what you use them for. If you get one, do a search on here for actifry related threads and take the advice contained in them. I own mine because my mother impulse purchased one, and didn't do her research before using it, ending up with some pretty crappy chips.
She has little patience for this sort of thing, lost interest, and gave it to me. I use it a lot, for all sorts of things, and its fab.